bpy_driver.c

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/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * Contributor(s): Willian P. Germano, Campbell Barton
 *
 * ***** END GPL LICENSE BLOCK *****
 */

/* ****************************************** */
/* Drivers - PyExpression Evaluation */

#include <Python.h>

#include "DNA_anim_types.h"

#include "BLI_listbase.h"
#include "BLI_math_base.h"

#include "BKE_fcurve.h"
#include "BKE_global.h"

#include "bpy_driver.h"

extern void BPY_update_rna_module(void);


/* for pydrivers (drivers using one-line Python expressions to express relationships between targets) */
PyObject *bpy_pydriver_Dict = NULL;

/* For faster execution we keep a special dictionary for pydrivers, with
 * the needed modules and aliases.
 */
int bpy_pydriver_create_dict(void)
{
    PyObject *d, *mod;

    /* validate namespace for driver evaluation */
    if (bpy_pydriver_Dict) return -1;

    d = PyDict_New();
    if (d == NULL)
        return -1;
    else
        bpy_pydriver_Dict = d;

    /* import some modules: builtins, bpy, math, (Blender.noise)*/
    PyDict_SetItemString(d, "__builtins__", PyEval_GetBuiltins());

    mod = PyImport_ImportModule("math");
    if (mod) {
        PyDict_Merge(d, PyModule_GetDict(mod), 0); /* 0 - dont overwrite existing values */
        Py_DECREF(mod);
    }

    /* add bpy to global namespace */
    mod = PyImport_ImportModuleLevel((char *)"bpy", NULL, NULL, NULL, 0);
    if (mod) {
        PyDict_SetItemString(bpy_pydriver_Dict, "bpy", mod);
        Py_DECREF(mod);
    }

    /* add noise to global namespace */
    mod = PyImport_ImportModuleLevel((char *)"mathutils", NULL, NULL, NULL, 0);
    if (mod) {
        PyObject *modsub = PyDict_GetItemString(PyModule_GetDict(mod), "noise");
        PyDict_SetItemString(bpy_pydriver_Dict, "noise", modsub);
        Py_DECREF(mod);
    }

    return 0;
}

/* note, this function should do nothing most runs, only when changing frame */
static PyObject *bpy_pydriver_InternStr__frame = NULL;
/* not thread safe but neither is python */
static float bpy_pydriver_evaltime_prev = FLT_MAX;

static void bpy_pydriver_update_dict(const float evaltime)
{
    if (bpy_pydriver_evaltime_prev != evaltime) {

        /* currently only update the frame */
        if (bpy_pydriver_InternStr__frame == NULL) {
            bpy_pydriver_InternStr__frame = PyUnicode_FromString("frame");
        }

        PyDict_SetItem(bpy_pydriver_Dict,
                       bpy_pydriver_InternStr__frame,
                       PyFloat_FromDouble(evaltime));

        bpy_pydriver_evaltime_prev = evaltime;
    }
}

/* Update function, it gets rid of pydrivers global dictionary, forcing
 * BPY_driver_exec to recreate it. This function is used to force
 * reloading the Blender text module "pydrivers.py", if available, so
 * updates in it reach pydriver evaluation.
 */
void BPY_driver_reset(void)
{
    PyGILState_STATE gilstate;
    int use_gil = 1; /* !PYC_INTERPRETER_ACTIVE; */

    if (use_gil)
        gilstate = PyGILState_Ensure();

    if (bpy_pydriver_Dict) { /* free the global dict used by pydrivers */
        PyDict_Clear(bpy_pydriver_Dict);
        Py_DECREF(bpy_pydriver_Dict);
        bpy_pydriver_Dict = NULL;
    }

    if (bpy_pydriver_InternStr__frame) {
        Py_DECREF(bpy_pydriver_InternStr__frame);
        bpy_pydriver_InternStr__frame = NULL;
        bpy_pydriver_evaltime_prev = FLT_MAX;
    }

    if (use_gil)
        PyGILState_Release(gilstate);

    return;
}

/* error return function for BPY_eval_pydriver */
static void pydriver_error(ChannelDriver *driver)
{
    driver->flag |= DRIVER_FLAG_INVALID; /* py expression failed */
    fprintf(stderr, "\nError in Driver: The following Python expression failed:\n\t'%s'\n\n", driver->expression);

    // BPy_errors_to_report(NULL); // TODO - reports
    PyErr_Print();
    PyErr_Clear();
}

/* This evals py driver expressions, 'expr' is a Python expression that
 * should evaluate to a float number, which is returned.
 *
 * (old)note: PyGILState_Ensure() isnt always called because python can call
 * the bake operator which intern starts a thread which calls scene update
 * which does a driver update. to avoid a deadlock check PYC_INTERPRETER_ACTIVE
 * if PyGILState_Ensure() is needed - see [#27683]
 *
 * (new)note: checking if python is running is not threadsafe [#28114]
 * now release the GIL on python operator execution instead, using
 * PyEval_SaveThread() / PyEval_RestoreThread() so we dont lock up blender.
 */
float BPY_driver_exec(ChannelDriver *driver, const float evaltime)
{
    PyObject *driver_vars = NULL;
    PyObject *retval = NULL;
    PyObject *expr_vars; /* speed up by pre-hashing string & avoids re-converting unicode strings for every execution */
    PyObject *expr_code;
    PyGILState_STATE gilstate;
    int use_gil;

    DriverVar *dvar;
    double result = 0.0; /* default return */
    char *expr = NULL;
    short targets_ok = 1;
    int i;

    /* get the py expression to be evaluated */
    expr = driver->expression;
    if ((expr == NULL) || (expr[0] == '\0'))
        return 0.0f;

    if (!(G.f & G_SCRIPT_AUTOEXEC)) {
        printf("skipping driver '%s', automatic scripts are disabled\n", driver->expression);
        return 0.0f;
    }

    use_gil = 1; /* !PYC_INTERPRETER_ACTIVE; */

    if (use_gil)
        gilstate = PyGILState_Ensure();

    /* needed since drivers are updated directly after undo where 'main' is
     * re-allocated [#28807] */
    BPY_update_rna_module();

    /* init global dictionary for py-driver evaluation settings */
    if (!bpy_pydriver_Dict) {
        if (bpy_pydriver_create_dict() != 0) {
            fprintf(stderr, "Pydriver error: couldn't create Python dictionary");
            if (use_gil)
                PyGILState_Release(gilstate);
            return 0.0f;
        }
    }

    /* update global namespace */
    bpy_pydriver_update_dict(evaltime);


    if (driver->expr_comp == NULL)
        driver->flag |= DRIVER_FLAG_RECOMPILE;

    /* compile the expression first if it hasn't been compiled or needs to be rebuilt */
    if (driver->flag & DRIVER_FLAG_RECOMPILE) {
        Py_XDECREF(driver->expr_comp);
        driver->expr_comp = PyTuple_New(2);

        expr_code = Py_CompileString(expr, "<bpy driver>", Py_eval_input);
        PyTuple_SET_ITEM(((PyObject *)driver->expr_comp), 0, expr_code);

        driver->flag &= ~DRIVER_FLAG_RECOMPILE;
        driver->flag |= DRIVER_FLAG_RENAMEVAR; /* maybe this can be removed but for now best keep until were sure */
    }
    else {
        expr_code = PyTuple_GET_ITEM(((PyObject *)driver->expr_comp), 0);
    }

    if (driver->flag & DRIVER_FLAG_RENAMEVAR) {
        /* may not be set */
        expr_vars = PyTuple_GET_ITEM(((PyObject *)driver->expr_comp), 1);
        Py_XDECREF(expr_vars);

        expr_vars = PyTuple_New(BLI_countlist(&driver->variables));
        PyTuple_SET_ITEM(((PyObject *)driver->expr_comp), 1, expr_vars);

        for (dvar = driver->variables.first, i = 0; dvar; dvar = dvar->next) {
            PyTuple_SET_ITEM(expr_vars, i++, PyUnicode_FromString(dvar->name));
        }
        
        driver->flag &= ~DRIVER_FLAG_RENAMEVAR;
    }
    else {
        expr_vars = PyTuple_GET_ITEM(((PyObject *)driver->expr_comp), 1);
    }

    /* add target values to a dict that will be used as '__locals__' dict */
    driver_vars = PyDict_New(); // XXX do we need to decref this?
    for (dvar = driver->variables.first, i = 0; dvar; dvar = dvar->next) {
        PyObject *driver_arg = NULL;
        float tval = 0.0f;
        
        /* try to get variable value */
        tval = driver_get_variable_value(driver, dvar);
        driver_arg = PyFloat_FromDouble((double)tval);
        
        /* try to add to dictionary */
        /* if (PyDict_SetItemString(driver_vars, dvar->name, driver_arg)) { */
        if (PyDict_SetItem(driver_vars, PyTuple_GET_ITEM(expr_vars, i++), driver_arg) < 0) {
            /* this target failed - bad name */
            if (targets_ok) {
                /* first one - print some extra info for easier identification */
                fprintf(stderr, "\nBPY_driver_eval() - Error while evaluating PyDriver:\n");
                targets_ok = 0;
            }
            
            fprintf(stderr, "\tBPY_driver_eval() - couldn't add variable '%s' to namespace\n", dvar->name);
            // BPy_errors_to_report(NULL); // TODO - reports
            PyErr_Print();
            PyErr_Clear();
        }
    }


#if 0 // slow, with this can avoid all Py_CompileString above.
    /* execute expression to get a value */
    retval = PyRun_String(expr, Py_eval_input, bpy_pydriver_Dict, driver_vars);
#else
    /* evaluate the compiled expression */
    if (expr_code)
        retval = PyEval_EvalCode((void *)expr_code, bpy_pydriver_Dict, driver_vars);
#endif

    /* decref the driver vars first...  */
    Py_DECREF(driver_vars);

    /* process the result */
    if (retval == NULL) {
        pydriver_error(driver);
    }
    else if ((result = PyFloat_AsDouble(retval)) == -1.0 && PyErr_Occurred()) {
        pydriver_error(driver);
        Py_DECREF(retval);
        result = 0.0;
    }
    else {
        /* all fine, make sure the "invalid expression" flag is cleared */
        driver->flag &= ~DRIVER_FLAG_INVALID;
        Py_DECREF(retval);
    }

    if (use_gil)
        PyGILState_Release(gilstate);

    if (finite(result)) {
        return (float)result;
    }
    else {
        fprintf(stderr, "\tBPY_driver_eval() - driver '%s' evaluates to '%f'\n", dvar->name, result);
        return 0.0f;
    }
}